1. Field
The disclosed concept pertains generally to electrical switching apparatus and, more particularly, to such electrical switching apparatus including an arc runner. The disclosed concept also pertains to arc runner assemblies including an arc runner. The disclosed concept further pertains to methods of manufacturing electrical switching apparatus including an arc runner.
2. Background Information
Electrical switching apparatus for power distribution systems include devices such as, for instance, circuit breakers, network protectors, transfer switches and disconnect switches. Circuit breakers, for example, typically include a number of stationary electrical contacts and a number of moveable electrical contacts. The stationary and moveable contacts are in physical contact with one another when it is desired that the circuit breaker provide current therethrough to a load. When it is desired to interrupt the circuit, however, the moveable contacts are moved away from the stationary contacts, thus removing the moveable contacts from physical contact with the stationary contacts and creating a space therebetween.
The movement of the moveable contacts away from the stationary contacts results in the formation of an electrical arc in the space between the contacts beginning at the time the contacts are initially separated. Such an arc is undesirable for a number of reasons. For example, current flows through the circuit breaker to the load when it is desired that no such current should flow thereto. Additionally, the electrical arc extending between the contacts often results in vaporization or sublimation of the contact material itself, eventually resulting in destruction or pitting of the moveable and stationary contacts. It is thus desired to eliminate any such arcs as soon as possible upon their propagation.
The moveable contacts typically are mounted on arms that are contained in a pivoting assembly which pivots the moveable contacts away from the stationary contacts. An arc chute can be provided along the path of each arm to break up and dissipate such arcs. Such arc chutes typically include a plurality of spaced apart arc plates mounted in a wrapper. As the moveable contact is moved away from the stationary contact, the moveable contact moves past the ends of the arc plates, with the arc being magnetically urged toward and between the arc plates. The arc plates are electrically insulated from one another such that the arc is broken up and extinguished by the arc plates. Examples of arc chutes are disclosed in U.S. Pat. Nos. 6,703,576; 6,297,465; 5,818,003; and 4,546,336.
It is known to employ an arc runner to drive an arc from a stationary contact to an arc chamber. See, for example, U.S. Pat. Nos. 4,229,630; 5,969,314; 6,417,474; and 6,452,470.
FIG. 1 shows an example of a known arc runner assembly in which a stationary contact 2 and an adjacent arc runner 4 are disposed on a line terminal conductor 6 of a circuit breaker (not shown). The arc runner 4 is secured to the line terminal conductor 6 by a screw 8. Whenever the circuit breaker movable contact (not shown) separates from the stationary contact 2, the resulting arc (not shown) may stall on the screw slot 10 and, thus, may not be promptly transferred to adjacent arc plates (not shown). Furthermore, this may result in the arc runner 4 blowing off of the line terminal conductor 6.
U.S. Patent App. Pub No. 2005/0279734 A1 discloses an arc runner that is fixedly retained to a conductor without the use of separate fastening hardware. Instead, the arc runner uses flexible legs that are bent or crimped in an installation step in order to secure the arc runner to the conductor. Although such design eliminates the need for separate fastening hardware, the design adds unwanted complexity to the design of the arc runner. Additionally, such design requires at least one additional step during installation of the arc runner.
There is a need, therefore, for electrical switching apparatus with an improved arrangement for extinguishing arcs generated during current interruption.
There is a more specific need for such an improved arrangement for directing the arc from a stationary contact into an arc chute.
Accordingly, there is room for improvement in electrical switching apparatus including arc runners.